High bandwidth probe assembly

ABSTRACT

A spring probe block assembly includes an insulative housing. A probe connector having a signal probe, an insulative layer, and a conductive shell is positioned within the housing. At least one ground probe is also positioned within the housing. The ground probe and the conductive shell of the probe connector are electrically connected by a grounding element. The grounding element is configured to elastically deform the ground probe in such a manner as to create spring energy in the ground probe. The spring energy generates a normal force between the ground probe and the grounding element which maintains the ground probe in its position. Also, a method for retaining a spring probe in a housing by elastically deforming the spring probe to maintain a spring force between the spring probe and the housing.

BACKGROUND OF THE INVENTION

The present invention relates to spring probe block assemblies of thetype used in Automatic Test Equipment (ATE), and specifically to springprobe block assemblies for use in high bandwidth applications.

Spring probe blocks are used to provide temporary spring contactinterfaces between integrated circuits or other electronic equipment andthe automated test to equipment test head to run necessary tests ofintegrated circuits or other electronic equipment. Spring probe blockassemblies of the type used in automatic test equipment are widelyavailable and use generally similar designs. Spring probe block housingsare typically machined from metal bar stock in a costly sequence ofprocesses that assure precise location and diameter of the bores thataccept press fitted coaxial probes and ground receptacles. The solidmetal fabrication also serves to commonly ground all of the circuitelements, which until recently was considered desirable from a signalintegrity perspective. Some spring probe block housings have also beenmade of a molded polymer instead of a machined metal.

With both the metal and polymer probe block housings, coaxial probeconnectors are individually terminated to coaxial cables at one end andto spring probes at the other. Typically, one spring probe is providedfor each signal line, and one or more spring probes are provided toserve as a reference (ground) for each signal line. In the case ofpolymer spring probe housings, coaxial shield tubes and ground springprobes associated with each signal line can be electrically isolatedfrom their neighbors by the dielectric material of the polymer housing.This isolation of each channel (consisting of a signal line plus itsassociated ground return loop) is necessary to achieve higherbandwidths. The ability to work at high bandwidths is important becausethe next generation of automated test equipment will be used not only totest faster integrated circuits, but also to test integrated circuitsmore quickly.

Many currently available spring probe block assemblies are not suitablefor use in high bandwidth applications because their designs suffer fromone or more infirmities. In particular, many of the prior art springprobe block assemblies (specifically those made using a metal housing)provide a common ground for all of the ground probes. As discussedabove, common grounding is not suitable for high bandwidth applications.Rather, for high bandwidth applications it is desired to have the signalprobe and its associated ground probes electrically isolated from othercoaxial signal and ground probes.

Many of the prior art designs (those using both metal and polymerhousings) are also unsuitable for use in high bandwidth applicationsbecause of the presence of excessively large ground return loops. FIG.1A shows a prior art spring probe block assembly 10 that utilizes apolymer housing 12. The ground probes 14 and the signal probe 16 areinserted through holes 18 in the front of the polymer housing 12, withthe ground probes 14 being received by box contacts 20. Box contacts 20are soldered to the coaxial connector 22, which terminates coaxial cable23 and receives the signal probe 16.

As is illustrated in FIG. 1B, the excessive length of the ground loop(illustrated by dashed line 30) limits the bandwidth because ofincreased inductance. The ground loop 30 runs from the tip of signalprobe 16, through ground probe 14 into box contact 20, along beams 32 ofbox contact 20, through the weld 34 and then along the conductive shield36 of the coaxial connector 22. The length of the ground loop isworsened by the thickness of the polymer housing 12 through which thesignal and ground probes 16, 14 must pass.

It is well known that at high speeds, the inductance of a given returncurrent path is far more significant than its resistance. In fact,high-speed return currents follow the path of least inductance, not thepath of least resistance. Further, it is well know that the lowestinductance return path lies directly under a signal conductor. Thismeans that minimizing the total ground loop length between the outgoingand returning current paths will lead to the lowest possible inductance.Thus, in FIG. 1B, an ideal ground loop is illustrated by dashed line 38.(See High Speed Digital Design: A Handbook of Black Magic by HowardJohnson and Martin Graham).

In addition to the above infirmities, many available designs of springprobe block assemblies require additional components or manufacturingsteps to retain the ground spring probe in the assembly. In someinstances, tubular receptacles for receiving and retaining the groundspring probes are used. For example, as shown in FIG. 2, in a metalspring probe block housing 40, after a bore 42 is machined into thehousing 40 a tubular metal receptacle 44 is press fit into the bore 42,and then the ground spring probe 46 is inserted into the receptacle 44where it is held in place by a press fit. The receptacle 44 is used toadd compliance to the system and avoid damage to the ground spring probe46, because the ground spring probe 46 itself has very littlecompliance. The use of probe receptacles 44 adds the undesirablerequirements of additional assembly steps and additional parts to beinventoried. In other instances where a tubular receptacle is not used,the ground spring probe is manufactured with what is referred to as a“banana bend”. The banana bend allows the ground spring probe to beinserted into an oversized bore and retained within the bore by africtional fit. However, manufacturing a spring probe with a banana bendis difficult and costly, and requires that different types of springprobes be used for the signal and ground lines. Clearly, the addedmanufacturing difficulty and cost, as well as the increased inventory isundesirable. In both of the above described situations, replacing adamaged ground spring probe if very difficult without damaging theremainder of the assembly.

Clearly, what is needed is a spring probe block assembly that canprovide a cost effective approach for providing electrically stable, lowinductance paths between coaxial connectors and their ground probes.Preferably, such a spring probe block assembly would eliminate the needfor ground probe receptacles (and their associated cost, assembly labor,and longer impedance path). In addition, the spring probe block assemblywould not require the used of a ground spring probe having a banana bendwhen no ground probe receptacle is used. Preferably, the spring probeblock assembly would also facilitate the replacement of spring probesand coaxial connectors within the block assembly without requiringextensive rework or even scrapping of the entire spring probe blockassembly. In addition, the spring probe block assembly would preferablybe resistant to high cable pullout forces that could inadvertentlydislodge the coaxial connectors during motion of the automated testequipment.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a cross-sectional view of a prior art spring probe blockassembly;

FIG. 1B is a greatly enlarged perspective view of the probe connectorand ground probe assembly of the spring probe block assembly of FIG. 1A;

FIG. 2 is a perspective view of another prior art spring probe blockassembly;

FIG. 3A is a perspective view of one embodiment of the inventive springprobe block assembly described herein;

FIG. 3B is an elevational view of the front face of the spring probeblock assembly of FIG. 3A;

FIG. 3C is a greatly enlarged view of a portion of the front face of thespring probe block assembly of FIG. 3A;

FIG. 4A is a cross-sectional view taken along line 4—4 of FIG. 3B;

FIGS. 4B and 4C are explodes and assembled views, respectively, of theground plate, probe connector and ground probes shown in FIG. 4A.

FIGS. 5A-5C are cross-sectional illustrations of alternate spring proberetention configurations;

FIG. 6A is a cross-sectional view of a spring probe block assemblyhaving optional vacuum sealing;

FIG. 6B is a perspective view of a molded insert for providing optionalvacuum sealing;

FIG. 7A is an elevational view of the front face of an alternateembodiment of the inventive spring probe block assembly describedherein;

FIG. 7B is a greatly enlarged view of the conductive retainer element ofFIG. 7A.

FIGS. 8A and 8B are perspective views of an alternate embodiment of theconductive retainer element of the spring probe block assembly describedherein;

FIG. 8C is a greatly enlarged view of the conductive retainer element ofFIGS. 8A and 8B.

FIGS. 9A and 9B are perspective views showing retainers used in theembodiments of FIG. 7A, 8A and 8B.

SUMMARY OF THE INVENTION

The present invention is a spring probe block assembly for use in highbandwidth applications. The spring probe block assembly described hereinelectrically isolates the signal probe and its associated ground probesfrom other coaxial signal and ground probes, and provides a lowinductance return path for the signal. The spring probe block assemblyalso eliminates the need for ground receptacles or spring probes whichutilize a banana bend.

In a preferred embodiment, the spring probe block assembly comprises aninsulative housing having a cavity in a front face of the housing. Aconductive retainer is positioned in the cavity adjacent the front faceof the housing. The conductive retainer has passages for receiving theprobe connector and the ground probes. The conductive retainerelectrically connects the ground probe and the conductive shell of thesignal probe connector to provide a low inductance ground return pathfor the associated signal. Preferably, the housing of the spring probeblock assembly is formed of a dielectric insulative material which haseither anti-static or static dissipative properties.

In one embodiment, the ground probes are retained within the conductiveretainer by a normal force which is generated when the ground probe isinserted into the retainer. The normal force is generated as the groundprobe is deflected by a ramped sidewall within the housing. As theground probe is deflected by the ramped sidewall, the ground probe isfrictionally retained in the assembly. In another embodiment, theinsertion of the ground probe into the retainer causes a clamping forceto be generated on the probe connector body, thereby retaining the probeconnector, retainer, and ground probes in a fixed relationship.

An additional aspect of the invention is a grounding element forelectrically connecting a ground probe with a cable shield of a signalprobe connector, wherein the ground probe is elastically deformed by thegrounding element to maintain a spring force between the groundingelement and the ground probe. The elastic deformation of the groundingelement may be created, for example, by providing a bore having anon-linear axis into which the ground probe is inserted. As the groundprobe is inserted into the bore having a non-linear axis, elasticdeformation of the ground probe causes a spring force to be created andthereby retain the ground probe in position.

Yet another aspect of the invention is a method for retaining a springprobe in a housing. The method comprises forming a bore having anon-linear axis in the housing, and then inserting a linear spring probeinto the bore. By inserting the linear spring probe into the non-linearbore, the spring probe is elastically deformed and maintains a springforce between the housing and the spring probe, thereby maintaining thespring probe in its position.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a cost effective approach for creatingelectrically stable, low inductance paths between coaxial connectors andtheir ground probes when used in spring probe block assemblies. Thespring probe block assembly described herein allows easy replacement ofcomponents of the spring probe block assembly, without requiringextensive rework or scrapping of parts. Further, the design is resistantto inadvertent dislodging of the coaxial connectors when they aresubject to high cable pullout forces during use.

FIG. 3A provides a perspective view of one preferred embodiment of thespring probe block assembly described herein. As seen in FIG. 3A, springprobe block assembly 50 includes a housing 52 which is formed, such asby injection molding, from a suitable insulative polymer material, suchas glass fiber reinforced polyphtalarnide (PPA). In some intendedapplications of the probe block assembly, it may be preferred to usepolymer materials that have anti-static properties, such as carbon fiberreinforced polyphtalamide. The housing 52 includes in its front face 53cavities 54 which are shaped to receive ground plates 56 in a slip orpress fit manner. The ground plates 56 are designed to receive andretain both ground spring probes 58 and probe connector 60. As can beseen more clearly in FIGS. 3B and 3C, the probe connector 60 includessignal spring probe 61 which is surrounded by dielectric insulation 62and then a conductive shield 64. The signal probe 61 is thus isolatedfrom ground. The conductive shield 64 of the probe connector 60 is inintimate contact with the ground plate 56. Ground spring probes 58 areslidably received within openings 66 in the ground plate 56 and makecontact with the ground plate 56 in a manner further described below. Ascan be seen, the dielectric material housing 52 surrounds and isolatesthe ground elements (ground plate 56 and ground spring probes 58) andtheir associated signal line from every other ground and signal linepairing. All grounds in the assembly are also insulated from other probeblock assemblies which may be adjacent, as well as from the automatedtest equipment chassis ground.

FIG. 4A shows a greatly enlarged cross-sectional view of the springprobe block assembly 50 with a single coaxial probe connector 60 and itsassociated signal and ground probes 61, 58, respectively. For additionalclarity, FIGS. 4B and 4C illustrate exploded and assembled views,respectively, of ground plate 56, ground spring probes 58 and probeconnector 60. As can be seen in FIG. 4A, the cavity 54 extends into thehousing 52 and conforms to the general envelope of an assembled set ofgrounding elements, with the cavity 54 dimensioned in such a manner asto constrain the axial and lateral movement of the assembled probeconnector 60, ground plate 56 and spring probes 58, 61. In particular,the ground plates 56 each have an opening 68 sized to receive conductiveshield 64 of probe connector 60 and retain it by press-fit, where theinterference between the probe connector 60 and the opening 58 in groundplate 56 preferably results in elastic deformation of the ground plate56. Permitting elastic deformation of the ground plate 56 is preferredbecause probe connector 60 has very little compliance, and making theground plate 56 compliant effectively doubles the number of compliantmembers from one to two. This permits the use of less stringenttolerances in the components, and therefore increases themanufacturability of the probe block assembly 50.

As discussed above, in high bandwidth applications it is desired toprovide a low inductance ground return path in the probe assembly. Thus,it is preferred to position the ground plates 56 as far forward aspossible in the housing 52 such that the ground return path is shortenedand maintained in close proximity to the signal path. Therefore, in apreferred embodiment, the ground plates 56 are seated in housing 52 suchthat the front faces 69 of the ground plates 56 are flush with the frontface 53 of housing 52. Alternately, front faces 69 of ground plates 56may protrude slightly forward of front face 53 of housing 52. Theseating depth of ground plates 56 may be controlled by the position ofshoulders 71 in the cavity 54.

The ground plates 56 are preferably symmetrical so they may be insertedinto the cavities 54 in the housing 52 without requiring a specificorientation. In addition, the ground plates 56 preferably have athickness sufficient to prevent significant bending of the ground springprobe bodies 74 in the area of the spring probe plunger travel when theground spring probe body 74 is deformed by contact with the ramped sidewall 72 of the housing 52. In a preferred design, the ground plates 56are provided with open channels 80 which bisect the ground spring probethru-holes 66 to enhance flow of plating process fluids through theholes 66 during the manufacturing process. The ground spring probethru-holes 66 are preferably spaced to compensate for the angulardisplacement of the ground spring probe tips 59 when the ground springprobe bodies are displaced by bending against the ramped side wall 72 ofthe housing 52 when they are inserted into the assembly. Further, theground spring probe tips 59 are preferably disposed at an angle withrespect to the axis of the signal probe connector 60 at an angle of 3degrees or less to minimize the internal contact resistance withinground spring probe 58 and to avoid increasing wear during prolongedcycling of the assembly.

As noted above, the ground plates 56 have at least one thru-hole 66sized to allow the slip-fit passage of a ground spring probe 58. Theground spring probes 58 seat against an end wall 70 of the cavity 54 inthe housing 52. Preferably, the cavity 54 in housing 52 includes aramped side wall 72 which progressively interferes with the groundspring probe body 74 during its insertion so that the interferencebetween the ground spring probe body 74 and the ramped side wall 72elastically deforms the ground spring probe body 74, as seen in FIG. 4A.The interference between the ground spring probe body 74 and the rampedside wall 72 maintains a normal force between the ground spring probebody 74 and the ground plate 56 at two points 76. An optional thirdpoint of contact 76′ may be obtained by increasing the slope of theramped side wall 72 to force the end of the ground spring probe body 74against the signal probe connector body shield 64.

Ground spring probe body 74 may be deflected and retained within groundplate 56 by means other than contact with ramped side wall 72 asdescribed above. Specifically, ground plate 56 may be provided with boregeometry for maintaining a normal force against the ground spring probe58 without the use of ramped side wall 72 in housing 52. As illustratedin FIG. 5A, ground plate 56 may have a first bore 80 extending fromfront face 200, and a second bore 82 extending from back face 201, wherefirst and second bores 80, 82 are slightly offset from each other. Asground spring probe body 74 is inserted from front face 200 into firstbore 80 and then into second bore 82, ground spring probe body 74 isdeflected, causing ground spring probe body to exert a normal forceagainst ground plate 56 and thereby be held in place by a frictionalfit. As illustrated in FIG. 5B, ground plate 56 may alternately havefirst bore 80′ extending from front face 200, and a second bore 82′extending from back face 201, where second bore 82′ is positioned at anangle relative to first bore 80. As described above, when ground springprobe body 74 is inserted from front face 200 into first bore 80′ andthen into second bore 82′, ground spring probe body 74 is deflected, anormal force results, and ground spring probe body 74 is held by africtional fit. As illustrated in FIG. 5C, ground plate 56 mayoptionally be formed from a front portion 86 and a back portion 88,where a first bore 80″ extends through front portion 86 from front face200, and a second bore 82″ extends through back portion 80 from backface 201. When assembled in the housing 52, front and back portions 86,88, respectively of the ground plate are aligned such that first andsecond bores 80″, 82″ are slightly offset from each other. Again, asground spring probe body 74 is inserted from front face 200 into firstbore 80″ and then into second bore 82″, ground spring probe body 74 isdeflected, a normal force is generated, and ground spring probe body 74is held by a frictional fit.

It will be recognized that the designs illustrated in FIGS. 5A-5C mayalso be used in probe assemblies that have metal housings and that donot use ground plates or retainers as described above. Specifically, thespring probe retention methods illustrated in FIGS. 5A-5C may be used inmetal housings to secure ground probes in the housing without the use ofreceptacles or the need for pre-formed “banana-bends” in the groundprobes. Those skilled in the art will recognize that eliminating theneed for receptacles or pre-formed banana-bends simplifiesmanufacturability and reduces the cost of the probe assemblies, and istherefore highly desirable.

Additional features may be provided to the spring probe block assembly.For example, the housing 52 may be provided with access holes 90 whichcommunicate with the ground probe body seats 70 to allow a tool (notshown) access to the back of the ground spring probe bodies 74. Suchtool access would facilitate ground spring probe removal, such as when aspring plunger breaks during use. Optional access holes 90 would besealed when used in applications requiring vacuum sealing of the device.Vacuum sealing may be accomplished by providing a removable plug forfilling access holes 90.

If vacuum sealing of a device is desired, optional sealing capabilitiesmay also be provided within the bore 104 of cavities 54, such as shownin FIGS. 6A and 6B. The sealing capabilities are preferably provided bya single molded insert 100 of pliable polymer that includes a collarportion 102 designed to fit within the bore 104 of the cavity at theback face of housing 52. As seen in FIG. 6A, when the probe connector 60is inserted into the housing 52, the probe connector 60 would press thecollar 102 of compliant insert 100 against the walls of bore 104 andthereby provide a reliable seal. In addition to the single molded insert100 shown in FIGS. 6A and 6B, it would also be possible to provideindividual collars or o-rings within each of the bores 104 of the cavity52 to provide sealing. However, the use of individual o-rings wouldgreatly increase the assembly time of the device, as well as be moreeasily displaced during insertion of the probe connector 60.

In the spring probe block assembly 50 described herein, the distancefrom the front face 53 of the housing 52 to the ground spring probecontact point 76 in the housing 52 is minimized and is close to zero.That is, the ground spring probe body 74 contacts the ground plate 56 asclose to the front face 53 of the housing as is possible, therebyresulting in a very low inductance ground path. As discussed above, alow inductance ground path is highly desired, and in fact required, formany high bandwidth applications. The prior art spring probe blockassemblies utilize much longer electrical paths, and therefore havehigher self inductance, rendering them unsuitable for high speed testingcapabilities.

The above described spring probe block assembly also has the advantageof being easy to assemble, rework and repair. Because the polymerhousing described herein utilizes compliant members to hold the springprobe bodies in place and in electrical contact with each other, it iseasy to assemble the spring probe block assembly or to replace thoseparts that may be worn out or broken. Thus, the spring probe blockassembly described herein not only eliminates parts which must bediscarded when damaged during the assembly process, it also allowsrelatively inexpensive parts to be replaced, rather than requiring theentire assembly to be discarded.

In applications where it is required that the spring probe blockassembly must be sealed against a vacuum, the present invention allowseffective sealing by locating sealing rings as described above in eachhousing cavity around each probe connector 60. The sealing compressionis maintained by the spatial relationships among the components. Sealingaround the ground probes 58 is not required, because the housing 52allows the vacuum seal to be placed behind the position of the groundprobes 58.

Alternate Embodiment

An alternate embodiment of a spring probe block assembly 150 is shown inFIG. 7A. The spring probe block assembly 150 includes an insulativehousing 152, signal probe contacts 161 and ground probe contacts 158,and probe connector retainers 156. As in the first described embodiment,the housing 152 is a molded dielectric material, where the dielectricmaterial surrounds and isolates the ground elements and associatedsignal line from every other signal line and ground pairing, and furtherinsulates all grounds in the assembly from other adjacent probe blockassemblies and the automated test equipment chassis ground. As describedabove, the cored cavities in both ends of the housing 152 conform to thegeneral envelope of an assembled set of ground elements, with thecavities dimensioned to constrain axial and lateral movement of theassembled probe connectors and ground clamps when the spring probes areinstalled therein.

As seen in FIG. 7A and 7B, probe retainer 156 comprises a pair ofstamped electrical ground clamps 180 which engage each other to form aclamping device to receive the signal probe connector 160 and groundprobes 158. The ground clamps 180 have centrally located loops 182 inaxial alignment and a pair of spring arms 184 extending from each of twoends. The ground clamp subassembly is preferably symmetrical, such thatit may be inserted into the cavity of the housing 152 without a specificorientation, thereby increasing the ease of assembly. The loops 182 ofthe ground clamps 180 are sized to receive a signal spring probeconnector 160 which is slidably engaged with a low insertion force (lessthan 7 lbs.). When ground spring probes 158 are inserted between thespring arms 184, the arms 184 are outwardly displaced and generate anormal force against the signal spring probe connector body 60, therebyretaining the assembled elements in place. Preferably, one of the loops182 of the ground clamps 180 is located behind the press ring 183 of thesignal probe connector 160, thereby improving the pullout resistance ofthe device.

In the embodiment of FIGS. 7A and 7B, the spring arms 184 of the groundclamps 180 are outwardly angled in a scissors-like manner such that whenground probe 158 is inserted therebetween a clamping force urges theground probe 158 against an axial groove 190 of the housing 152, therebyestablishing the proper alignment of the ground probe 158 within thehousing 152. The included angle θ defined by the spring arms 184 ispreferably greater than 22 degrees. In addition, the side walls of thecavity in the housing preferably support the spring arms 184 of theground clamps 180 in a preloaded condition, such that the preload on thespring arms 184 increases the open area between the spring arms 184,thereby facilitating the insertion of the ground probe 158. Such preloadalso would increase the entry angle between the spring arm lead-inchamfers 192, thereby decreasing the required insertion force.

In an alternate embodiment shown in FIGS. 8A and 8B, the spring arms184′ of the ground clamps 180′ are curved back toward each other so asto substantially surround the ground probe 158 when ground probe 158 isinserted into the ground clamps 180′. When a ground probe 158 isinserted into the ground probe-receiving portion of the ground clamps180′, a clamping force tightens the ground clamps 180′ about the body ofsignal probe connector 160. If desired, the individual ground clamps180′ may be formed with optional connecting webs which allow the simplefolding of the ground clamps 180′ to obtain the final orientation of theelements. The optional connecting web securing the ground clampstogether may be frangible, if desired, or may be malleable.

To increase the cable pullout force, retainers 200 are preferablyprovided which secure to the back face 184 of the housing 152 in asnap-fitting arrangement, as seen in FIGS. 9A and 9B. The retainers 200preferably have latching arms 202 to engage reciprocal latching features204 of the housing 152. For ease of assembly, the retainers 200 wouldpreferably be formed as two pieces that have mating tongues 204 andgrooves 206 that interlock the two retainer pieces 200 together.Further, the housing 152 would preferably have an offset cavity in theback end of the housing with respect to the pattern of cavities thataccept the probe connectors, thereby allowing the use of identicalretainer parts. This would reduce the cost of manufacture and increasethe ease of assembly of the device. Preferably, the housing 152 wouldinclude passageways 208 that open to the latching arms 202 of theretainers 200, such that the retainers 200 may be disengaged from theoutside of the housing 152 for rework on the device.

For the embodiments of the spring probe block assemblies 50, 150described herein, those skilled in the art will recognize additions andmodifications that may be made without departing from the spirit andscope of the invention. For example, the housing 52, 152 of the assemblywill preferably be provided with mounting holes 210 so that the springprobe block assemblies 50, 150 may be mounted in an automated testequipment head. It is anticipated that the retainer elements (groundplates 56 and ground clamps 180, 180′) may have shapes that differ fromthose illustrated herein, or may, for example, be used in metal probeassembly housings, yet still embody the function and spirit of theinvention.

What is claimed is:
 1. A spring probe block assembly comprising: aninsulative housing hating a cavity in a front face of the housing; aprobe connector in the cavity, the probe connector having a signal probesurrounded by an insulative layer and a conductive shell; a conductiveground probe in the cavity; a conductive retainer positioned within thecavity adjacent the front face of the housing, the retainer havingpassages for receiving the probe connector and the ground probe, whereinthe ground probe is in electrical contact with the conductive retainerand the conductive shell of the probe connector.
 2. The spring probeblock assembly of claim 1, wherein the signal probe and ground probe arespring probes.
 3. The spring probe block assembly of claim 1, whereinthe housing is a molded dielectric material.
 4. The spring probe blockassembly of claim 3, wherein the dielectric material has anti-staticproperties.
 5. The spring probe block assembly of claim 3, wherein thedielectric material has static-dissipative properties.
 6. The springprobe block assembly of claim 1, wherein the housing includes aplurality of cavities, each of the plurality of cavities containing aconductive retainer, a probe connector and a ground probe.
 7. The springprobe block assembly of claim 1, further comprising a second conductiveground probe in the cavity.
 8. The spring probe block assembly of claim1, wherein the conductive retainer receives the probe connector bypress-fit, and wherein the conductive retainer receives the ground probeby slip-fit.
 9. The spring probe block assembly of claim 1, wherein thecavity includes a ramped side wall positioned such that the ground probeis deflected by the ramped side wall to create a normal force betweenthe ground probe and the retainer, thereby retaining the ground probewithin the assembly.
 10. The spring probe block assembly of claim 9,wherein the ground probe is electrically connected to the conductiveshell of the signal probe.
 11. The spring probe block assembly of claim1, wherein the ground probe is disposed at an angle relative to theprobe connector of three degrees or less.
 12. The spring probe blockassembly of claim 1, further comprising access holes in the housing, theaccess holes extending from an outer surface of the housing into thecavity at a point adjacent a back end of the ground probe.
 13. Thespring probe block assembly of claim 1, wherein the retainers aresymmetrical about at least one plane.
 14. The spring probe blockassembly of claim 1, wherein the cavity extends through the housing fromthe front face of the housing to a back face of the housing.
 15. Thespring probe block assembly of claim 1, wherein the ground probe is inelectrical contact with the conductive retainer at a point adjacent -thefront face of the housing.
 16. The spring probe block assembly of claim1, wherein the probe connector is a coaxial probe connector.
 17. Thespring probe block assembly of claim 1, wherein the retainer is formedfrom metal by a method selected from one of the group of machining,extruding, casting, metal injection molding, or sintering.
 18. Thespring probe block assembly of claim 1, wherein the retainer is formedfrom stamped sheet metal.
 19. The spring probe block assembly of claim1, wherein the retainer is formed from a conductive polymer.
 20. Thespring probe block assembly of claim 1, wherein the retainer is formedfrom a plated polymer.
 21. The spring probe block assembly of claim 1,wherein the probe connector is terminated to a coaxial cable adjacentthe back face of the housing.
 22. The spring probe block assembly ofclaim 1, wherein a resilient seal is positioned about the probeconnector adjacent a back end of the probe connector.
 23. A spring probeblock assembly comprising: a housing; a first probe connector positionedwithin the housing, the first probe connector having a signal probe, aninsulative layer, and a conductive shell; a first ground probepositioned within the housing; a first grounding portion electricallyconnecting the first ground probe and the conductive shell of the firstprobe connector; wherein a retention force is maintained between thefirst grounding portion and the first ground probe by spring energystored in the first ground probe by elastic deformation of the firstground probe.
 24. The spring probe block assembly of claim 23, whereinthe first grounding portion is electrically commoned with the housing.25. The spring probe block assembly of claim 23, wherein the firstgrounding portion is electrically isolated from the housing.